In the first place, it is to be noted that uttering takbir (Allahu Akbar) in prayer is either mandatory (wajib) or recommended. The mandatory takbir is the one that is uttered at the beginning of the prayer and is known as takbirat al-ihram. The recommended takbir is the one when making ruku’ (bowing down) and when prostrating and standing up from it, after the first Tashahhud (testification of faith) i.e. while standing up to start the third rak`ah.
The prominent Muslim scholar Sheikh `Atiyyah Saqr, former Head of Al-Azhar Fatwa Committee stated that: “Raising hands in prayer is not mandatory; rather, it is only a sunnah (recommended act). This ruling applies to raising hands which happens on four occasions, at the beginning of the prayer when uttering takbirat al-ihram (the opening takbir), when going down to ruku’, when standing up straight after ruku’ and after finishing the first Tashahhud while standing up to start the third rak`ah.”
Based on the above, it is to be concluded that raising one’s hands whether after ruku’ or elsewhere in prayer is NOT MANDATORY, it is only a recommended act of prayer.